The objectives of the study are: To assess the effects on tests of intelligence and behavior of phenobarbital, a commonly prescribed anticonvulsant in children. The design of this study will permit comparison of measures of tested intelligence and of behavior in children with febrile seizures who have been treated with phenobarbital and in a group of seizure free control children. A comparison of the groups should allow assessment of benefit and risk of treatment for a common childhood neurologic problem. (This study supports the DNB/DCDND/NINCDS contract study entitled: "Behavioral and cognitive side effects of phenobarbital used for prevention of febrile seizure recurrence." The project officer is Dr. Deborah G. Hirtz, DNB, DCDND, NINCDS, and the contractor of the study is the University of Washington.)